How to Write a Complaint Letter

A formal complaint letter should be clearly structured. Use the following format as a guide:

• Your contact details — name, address, email, phone number, and account or reference number
• Date
• Recipient details — the company's name and complaints address (or email)
• Subject line: "Formal Complaint — [Product/Service/Issue]"
• Opening paragraph: State that you are making a formal complaint and give a brief summary of the issue
• Facts paragraph(s): Set out the relevant facts in chronological order, with specific dates and amounts
• Impact paragraph: Describe how the issue has affected you — financially, emotionally, or in terms of time and inconvenience
• Resolution paragraph: State clearly what you want the company to do
• Deadline: Give a reasonable deadline for a response
• Closing: Sign off formally ("Yours faithfully" if you do not know the recipient's name; "Yours sincerely" if you do)

Certain phrases signal clearly that you are making a formal complaint and that you know your rights. Consider using phrases like:

• "I am writing to make a formal complaint about..."
• "This is contrary to the terms of my contract dated [date], specifically clause [X]."
• "Your failure to resolve this matter amounts to a breach of the Consumer Rights Act 2015."
• "I require a full written response within [X] days."
• "If I do not receive a satisfactory response by [date], I will refer this matter to [ombudsman/regulator/small claims court]."
• "I am happy to discuss this matter if it would assist in reaching a resolution."

Avoid threatening legal action unless you genuinely intend to pursue it — empty threats undermine your credibility. Similarly, avoid abusive or aggressive language, which can give the organisation grounds to treat your complaint as vexatious.

If your initial complaint has not been resolved satisfactorily, your follow-up or escalation letter should reference your previous correspondence and explain why the response was inadequate. Include:

• The date of your original complaint and your complaint reference number
• A brief summary of the company's response (or lack of it)
• Why their response is inadequate — for example, it does not address the key issue, the compensation offered is insufficient, or important facts were ignored
• Your revised or confirmed request for resolution
• An explicit statement that if this is not resolved, you will refer to the relevant ombudsman (naming them specifically)

Email is the preferred method for most complaints — it is instant, provides a date-stamped record, and is easy to search and forward. When emailing a complaint:

• Use the subject line "Formal Complaint — [Brief Description]"
• Request a read receipt if your email client supports it
• Attach documents as PDFs rather than image files where possible
• Keep your email concise — attach any lengthy supporting documents rather than pasting them into the email body

If you are sending by post, use recorded delivery so you have proof of receipt. Keep a dated copy of everything you send.

If the company has a specific complaints email address or online complaints form, use that rather than a general customer service address — complaints submitted through the correct channel are more likely to be logged properly and trigger the regulatory response clock.